1. Field of the Invention
The invention relates to a method for optimizing the load level on connection sections for VBR traffic that has ATM cells which are associated with VBR traffic and are transmitted between at least one transmitting device and at least one receiving device via common connection sections, and whose frequency is measured on a connection specific basis.
2. Description of the Related Art
A number of connection types are defined for connections via which information is transmitted using an asynchronous transfer mode (ATM). For example, connections which are used to transmit information at a constant bit rate (CBR) are distinguished from connections via which information is transmitted at a variable bit rate. VBR connections are connections via which low-priority information is transmitted between a transmitting device and a receiving device.
To achieve this, one might implement a system in whichxe2x80x94therefor; control cells are inserted in a timed pattern into the stream (originating from the transmitting device) of ATM cells associated with a connection. As a rule, the control cells could be inserted for every 32nd ATM cell. The ATM cells are then supplied together with the control cells to the receiving device in question. The latter removes from the cell stream those ATM cells carrying the wanted information. In addition to this, the control cells are removed and are fed back to the transmitting device together with connection-related data as well as data described in the current status of the connection sections. In the transmitting device, the connection-related information is removed from the control cells and, if necessary, the transmission rate is adapted.
In order to control these processes, the information portion of the control cells contains a field ER (Explicit Rate Field) to which information is written which is determined from a specific control method.
The proposal to the ATM Forum 96-1172 proposes that ATM cells associated with VBR traffic be controlled on the basis of a control method (ERICA) disclosed there. This is based on a minimum cell rate of MCR=0. This means that the explicit rate ER calculated by the control method (ERICA) is independent of the minimum cell rate MCR although this is actually a special case for a large number of transmissions.
The document xe2x80x9cMeasurement-Based Flow Control for VBR Services in ATM Networks, Nasir Ghani, John W. Mark, Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1-Canada, Vol. 8, No. 1, January-February 1997xe2x80x9d discloses a method describing how the measurement of ATM cells allows the network to be utilized better. In this case, fairness is desired, although this is not proportional to the minimum cell rate MCR. However, this results in a specific type of fairness, which is not always efficient in practical situations.
The document xe2x80x9cAllocating Fair Rates for Available Bit Rate Service in ATM Networks, Ambalavanar Arulambalam and Xiaoquiang Chen, Bell Laboratories Nirwan Ansari, New Jersey Institute, of Technology; IEEE Communications Magazine, November 1996xe2x80x9d, likewise discloses a method for bandwidth assignment. Once again, the known Erika algorithm is referred to, which is useable only to a limited extent in overload situations.